HDRenderPipeline: update comment + remove unsued _DirShadowSplitSpheres

ScriptableRenderPipeline/Core/CoreRP/ShaderLibrary/ImageBasedLighting.hlsl

         {
             // Integral{BSDF * <N,L> dw} =
             // Integral{(F0 + (1 - F0) * (1 - <V,H>)^5) * (BSDF / F) * <N,L> dw} =
-            // F0 * Integral{(BSDF / F) * <N,L> dw} +
-            // (1 - F0) * Integral{(1 - <V,H>)^5 * (BSDF / F) * <N,L> dw} =
+            // (1 - F0) * Integral{(1 - <V,H>)^5 * (BSDF / F) * <N,L> dw} + F0 * Integral{(BSDF / F) * <N,L> dw}=
             // (1 - F0) * x + F0 * y = lerp(x, y, F0)
 
             acc.x += weightOverPdf * pow(1 - VdotH, 5);

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Lighting/LightLoop/LightLoopDef.hlsl

 uint _PunctualLightCount;
 uint _AreaLightCount;
 uint _EnvLightCount;
-float4 _DirShadowSplitSpheres[4]; // TODO: share this max between C# and hlsl
-
-
 CBUFFER_END
 
 // LightLoopContext is not visible from Material (user should not use these properties in Material file)